Genetic information in living organisms is contained in the form of very long nucleic acid molecules such as deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Naturally occurring DNA and RNA molecules are typically composed of repeating chemical building blocks called nucleotides which are in turn made up of a sugar (deoxyribose or ribose, respectively), phosphoric acid, and one of four bases, adenine (A), cytosine (C), guanine (G), and thymine (T) or uracil (U). The first sequences of DNA (deoxyribonucleic acid) molecules were reported in the early 1970's. The human genome contains more than 3 billion base pairs of DNA. The first whole human genome sequence for an individual was not obtained until 2003, thirty years after the first sequences of DNA were obtained. This first sequence of an entire genome of a human cost about $2.7 billion dollars and took more than ten years to accomplish (according to the National Human Genome Research Institute). Knowledge of an individual's entire genome provides tremendous opportunities to target therapies and medical treatments to individuals most likely to benefit and to understand the molecular basis of many diseases. Forty years after the first DNA molecule was sequenced, the search for a technique that would allow an entire human genome to be rapidly and accurately sequenced cost effectively remains an elusive target.